Elephantin

3-Methyl-2-butenoic acid [(1aR,3R,8S,8aR,11aS,11bR)-1a,2,3,7,8,8a,9,10,11a,11b-decahydro-1a-methyl-9-methylene-5,10-dioxo-5H-3,6-methenofuro[2,3-f]oxireno[d]oxacycloundecin-8-yl] ester